https://www.compellingtruth.org/soul-sleep.html
Is "soul sleep" a biblical concept?
"Soul sleep" is the belief that the souls of Christians who die will "rest" in an inert state until Christ's future return. Soul sleep is also called Christian mortalism or psychopannychism. The idea of soul sleep has been held by a variety of religious groups throughout history including the Seventh-day Adventist Church, Christadelphians, and Jehovah's Witnesses (with a variation for a special group of 144,000).
The Bible presents a clear view of what happens to the soul at the point of death. The apostle Paul taught that when a Christian's life ends on this earth, he or she is immediately in the presence of the Lord.
Second Corinthians 5:8 says, "we would rather be away from the body and at home with the Lord." Paul later noted in
Philippians 1:23 that his desire was to "depart and be with Christ."
Another important biblical passage that refutes soul sleep can be found in
Luke 16:19-31. Jesus taught that both a rich man and a poor man named Lazarus died. The rich man immediately received eternal punishment and Lazarus immediately received eternal life. The context of the passage points out that Lazarus was conscious at Abraham's side (v. 23).
A third example can be found in the account of the thief on the cross. In
Luke 23:43, Jesus promised this man that
today he would be with Jesus in paradise. How else could this reference to "today" be understood than being the same day Jesus was talking with this man?
In contrast, those who hold to the view of soul sleep often refer to
Revelation 6:9 to support their view. It states, "I saw under the altar the souls of those who had been slain for the word of God and for the witness they had borne." This passage refers to the souls of those killed during the Tribulation who were now in the presence of the Lord. They had not yet received their resurrection bodies (mentioned later in Revelation), but they were active, in conversation, and in God's presence after death.
While there are some areas of dispute regarding the details of what happens to a Christian's soul upon death, the Bible's clear teaching regarding the state of the believer reveals that to be apart from the body is to be with the Lord. Therefore, the view of soul sleep, which places an extended period of time after death before a believer is present with the Lord, is clearly at odds with the teachings of Scripture.